Abstract

The magnetization processes in exchange-biased bilayers have been investigated using polarized neutronreflectivity and vibrating sample magnetometry. The measurements show that by breaking the symmetry of the intrinsic cubic fourfold anisotropy of the Fe film the induced unidirectional anisotropy radically changes the magnetization processes. If the exchange bias is large the induced unidirectional anisotropy is able to pull the net magnetization of the sample to the bias direction after saturation along any of the magnetic hard Fe⟨110⟩ directions. However, if the exchange bias is small it will only give rise to a difference in net magnetization along the magnetic easy axes adjacent to the saturation direction. Thus, the net magnetic moment along the bias direction depends on the relative magnitudes of the cubic and the unidirectional anisotropies.

Received 29 April 2004Accepted 20 August 2004Published online 22 November 2004

Acknowledgments:

This work was supported by the Department of Energy, Materials Science Division, under Grant No. DE-FG03-02ER45987 and by the Campbell Endowment at UW. Work at Argonne was supported by US Department of Energy, Office of Science, under Contract No. W-31-109-ENG-38. The authors would like thank David E. McCready at the EMSL∕Pacific Northwest National Laboratory for the help with the XRD measurements.